Ph. Kaufmann et al., Influence of day and night temperature differentials on root elongation rate, root hydraulic properties, and shoot water relations in chrysanthemum, J AM S HORT, 125(3), 2000, pp. 383-389
Citations number
24
Categorie Soggetti
Plant Sciences
Journal title
JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE
The difference between night and day temperature (DIF = day - night tempera
ture) has been shown to affect plant height. A positive DIF (+DIF), cooler
night than day temperature, increases stem elongation while a negative DIF
(DIF), warmer night than day temperature, decreases stem elongation. The ph
ysiological mechanism underlying the growth response to DIF is not understo
od, however, and the effects of day/night temperature differentials on root
permeability to mater and root elongation rate have not been studied. The
objective of this study was to describe how +DIF and -DIF temperature regim
es affect leaf water relations, root water flux (J(v)), root hydraulic cond
uctivity (L-p), and root elongation rates of 'Boaldi' chrysanthemum [Dendra
nthema xgrandiflora Kitam,'Boaldi' (syn, Chrysanthemum xmorifolium Ramat.)]
plants over time. Leaf turgor pressure (psi p) was 0.1 to 0.2 MPa higher i
n plants grown in a +6 degrees C DIF environment throughout both the Light
and dark periods, relative to those in a -6 degrees C DIF environment, J(v)
differed markedly in roots of plants grown in +DIF vs -DIF environments, R
hythmic diurnal patterns of J(v) were observed in all DIF treatments, but t
he relative timing of flux minima and maxima differed among treatments. Pla
nts grown in positive DIF regimes exhibited maximum root flux at the beginn
ing of the light period, while those in negative DIF environments had maxim
um root nux during the first felv hours of the dark period. Plants grown in
+DIF had significantly higher L-p than -DIF plants. Plants grown in +DIF a
nd -DIF environments showed differences in the diurnal rhythm of root elong
ation. During the dark period, +DIF plants exhibited minimal root elongatio
n rates, while -DIF plants exhibited maximal rates. During the light period
, the converse was observed. In -DIF temperature regimes, periods of rapid
root elongation coincided with periods of high J(v). Results of this study
suggest that negative DIF environments lead to leaf turgor reductions and m
arkedly alter diurnal patterns of root elongation These changes may, in tur
n, act to reduce stem elongation.